The present invention relates to an exhaust back pressure control system for an internal combustion engine, particularly a diesel engine, to improve engine warmup upon starting in a cold environment. The control system incorporates a valve assembly mounted at the turbine discharge outlet of a turbocharger, the position of which is controlled by a microcomputer through an electrically controlled hydraulic valve using engine lubricating oil pressure to provide a controlled increase of exhaust back pressure on the engine during cold start conditions, thereby decreasing the warm-up period for the engine.
Due to the increased efficiency and lower combustion chamber surface-to-volume ratio, direct injection diesel engines are inherently slower to warm up than indirect injection engines. The increase in back pressure provides an artificial load to the engine which creates a greater friction therein, causing a quicker engine warm-up and improved heating of the cab of the vehicle.